8051 Programming syntax error problem

[Embedded_Geek]

When i specified the macro "#define" the program is not getting compiled. It is showing syntax error in the following statement
RS=0;
RW=0;
EN=1;
The full code is

#include<reg51.h>
#define RS P2^0
#define RW P2^1
#define EN P2^2
sfr ldata=0x90;
void lcdcmd(unsigned char value);
void lcddata(unsigned char value);
void MSDelay(unsigned int itime);


void main()
{ 
  lcdcmd(0x38);
  MSDelay(250);
  lcdcmd(0x0E);
  MSDelay(250);
  lcdcmd(0x01);
  MSDelay(250);
  lcdcmd(0x06);
  MSDelay(250);
  lcdcmd(0x86);
  MSDelay(250);
  lcddata('M');
  MSDelay(25);
  lcddata('D');
  MSDelay(25);
  lcddata('E');
  while(1);
  }

void lcdcmd(unsigned char value)
{
	ldata=value;
	RS=0;
	RW=0;
	EN=1;
	MSDelay(1);
	EN=0;
	
}

void lcddata(unsigned char value)
{
	ldata=value;
	RS=1;
	RW=0;
	EN=1;
	MSDelay(1);
	EN=0;
	
}

void MSDelay(unsigned int itime)
{
	unsigned int i,j;
	for(i=0;i<itime;i++)
	for(j=0;j<1275;j++);
}

 

[keith1200rs]

I don't use the 8051 but #defines are fixed - you cannot then change them in your program as you are trying to do.

Keith

 

[Embedded_Geek]

as u can see the value is not changed in my program.

 

[keith1200rs]

as u can see the value is not changed in my program.

But it is. At the top you make RW equal P2^1 and later you try to say RW=0.

Once you #define something you can only use it, not change it.

Keith

Added after 6 minutes:

It might work if you put quotes round it - #define RW "P2^1" but I am not a C expert.

Keith

 

[Embedded_Geek]

for example in my program i have used rs in my program. during compiling "rs" will simply be replaced by P2^0. When i use P2_0 instead of P2^0 then it works fine. I cannot understand what the problem is.

 

[keith1200rs]

Sorry, it is out of my area of expertise. Maybe it is specific to your compiler or 8051.

Keith

 

[Kevin.Lee]

Hi, there is a way for your application.

if you are coding in Keil, then using below code to instead of your,

#include<reg51.h>
sbit RS = P2^0;
sbit RW = P2^1;
sbit EN = P2^2;
//..........

 

[Embedded_Geek]

if you are coding in Keil, then using below code to instead of your,

#include<reg51.h>
sbit RS = P2^0;
sbit RW = P2^1;
sbit EN = P2^2;
//..........

yeah that works fine. But i want to know why #define is causing problem.

 

[BurnOut_tesla]

hey just have look at ur reg51.h file
How zeroth or any corresponding bit of any port is associated and written in that header file..
this will solve ur problem n ll avoid ur confusion....

 

[GrandAlf]

Ajishgopair has the solution, below is example driver.

#include <reg51.h>
#include "delay.h"

sbit LCD_RS =P1^0; // Register select
sbit LCD_E =P1^1; // Enable

#define LCD_STROBE ((LCD_E = 1),(LCD_E=0))


// Time in Milliseconds
void DelayMs(unsigned char cnt)
{ cnt=2*cnt;
do
{DelayUs(500);}
while(--cnt != 0);
}

// Send to Display
void lcd_write(unsigned char c)
{
unsigned char Movit;
Movit = (c >> 2);
P1 = (P1 & 0xC3) | (Movit & 0x3C);
LCD_STROBE;
Movit = (c << 2);
P1 = (P1 & 0xC3) | (Movit & 0x3C);
LCD_STROBE;
DelayUs(60);
}

// Clear and home the LCD
void lcd_clear(void)
{
LCD_RS = 0;
lcd_write(0x80);
DelayMs(2);
}

// Position the Cursor
void lcd_goto(unsigned char pos)
{
LCD_RS = 0;
lcd_write (0x80+pos);
}

// Send Character String
void lcd_puts(const char * s)
{
unsigned char cursor = 0x00;

while(*s)
{
LCD_RS = 1;
lcd_write(*s);
s++;
cursor++;
if (cursor==0x08)lcd_goto(0x40); // Change to 0x80 for simulation
if (cursor==0x10){cursor=0;lcd_goto(0x00);}
}
}


// Initialise the LCD - mode 4 bits
void lcd_init(void)
{
LCD_RS = 0;
DelayMs(20); // power on delay
lcd_write(0x28); // 4 bit mode, 1/16 duty, 5x8 font
LCD_STROBE;
DelayMs(3);
LCD_STROBE;
DelayMs(3);
LCD_STROBE;
lcd_write(0x28);
lcd_write(0x08); // display off
lcd_write(0x0C); // display on, cursor off
lcd_write(0x06); // entry mode
}